Pivot bush

Abstract

A plastic pivot bush for swingably holding upper and lower spherical surface portions with respect to an equator of a spherical pivot, includes an upper concave spherical surface, a main body connected onto the upper concave spherical surface to enclose the remaining portion of the spherical pivot and having therein a cylindrical surface with a lower end thereof opened up, and an elastic thin piece originating from the boundary between the upper concave spherical surface and the cylindrical surface and provided with an opening at the center of a lower portion thereof. The elastic thin piece is split into a plurality of pieces by a plurality of slits extending in the longitudinal direction. The main body has at an outer periphery thereof an annular groove engageable with a mounting hole of the arm.

What is claimed is: 
     
       1. A pivot bush made of a plastic material for swingably holding upper and lower spherical surface portions with respect to an equator of a spherical pivot, said pivot bush comprising an upper concave spherical surface corresponding at least to a portion of the upper spherical surface portion above the equator of the spherical pivot, a main body connected onto said upper concave spherical surface to enclose the remaining portion of said spherical pivot under the equator and having therein a cylindrical surface with a lower end thereof opened up, and a bowl shaped elastic thin piece originating from a boundary between said upper concave spherical surface and said cylindrical surface and provided with an opening at the center of a lower portion thereof, an inner surface of the elastic thin piece forming a lower concave spherical surface corresponding to a part of said lower spherical surface portion under the equator of said spherical pivot, said elastic thin piece being split into a plurality of pieces by a plurality of slits which extend in the longitudinal direction and are formed by cutting the elastic thin piece from the opening of the center of the lower portion thereof, said main body having at an outer periphery thereof an annular groove engageable with a marginal portion of a mounting hole of an arm along the boundary between said upper concave spherical surface and said cylindrical surface. 
     
     
       2. A pivot bush as claimed in claim 1, wherein the lower end of the opening of the lower portion of said elastic thin piece is higher than the lower end of said cylindrical surface of said main body. 
     
     
       3. A pivot bush as claimed in claim 1, wherein, of the slits splitting said elastic thin piece in the longitudinal direction, the upper ends of the slits at the position perpendicular to the operating direction of the arm are set to be above the boundary between said upper concave spherical surface and said cylindrical surface, while the upper ends of the remaining slits are set to be under said boundary. 
     
     
       4. A pivot bush as claimed in claim 1, wherein said mounting hole of the arm includes a cut-out extending in the operating direction thereof. 
     
     
       5. A pivot bush as claimed in claim 1, wherein said bush is molded of a thermoplastic synthetic resin material so that an annular groove thereof is engaged in said mounting hole of the arm. 
     
     
       6. A pivot bush made of plastic material for swingably holding upper and lower spherical surface portions with respect to an equator of a spherical pivot, said pivot bush comprising an upper concave spherical surface corresponding at least to a portion of the upper spherical surface portion above the equator of the spherical pivot, a main body connected onto said upper concave spherical surface to enclose the remaining portion of said spherical pivot under the equator and having therein a cylindrical surface with a lower end thereof opened up and an elastic thin piece originating from a boundary between said upper concave spherical surface and said cylindrical surface and provided with an opening at the center of a lower portion thereof, an inner surface of the elastic thin piece forming a lower concave spherical surface corresponding to a part of said lower spherical surface portion under the equator of said spherical pivot, the lower end of the opening of the lower portion of said elastic thin piece is higher than the lower end of said cylindrical surface of said main body, said elastic thin piece being slit into a plurality of pieces by a plurality of slits which extend in a longitudinal direction and are formed by cutting the elastic thin piece from the opening of the center of the lower portion thereof, said main body having at an outer periphery thereof an annular groove engageable with a marginal portion of a mounting hole of an arm along the boundary between said upper concave spherical surface and said cylindrical surface, said slits splitting said elastic thin piece in the longitudinal direction, the upper ends of the slits at the position perpendicular to the operating direction of the arm are set to be above the boundary between said upper concave spherical surface and said cylindrical surface, while the upper ends of the remaining slits are set to be under said boundary. 
     
     
       7. A pivot bush as claimed in claim 7, wherein the said mounting hole of the arm includes a cut-out extending in the operating direction thereof. 
     
     
       8. A pivot bush as claimed in claim 6, wherein said bush is molded of a thermoplastic synthetic resin material so that an annular groove thereof is engaged in said mounting hole of the arm.